Along with continuous improvement of the technology of display panel and its manufacturing process, the research on integrating the function of a touch panel with a liquid crystal panel becomes increasingly popular. As compared with a traditional method of arranging the touch panel on the liquid crystal panel, the integration technologies of a built-in touch panel mainly include two different types: on-cell touch and in-cell touch. The difference between the on-cell touch and the in-cell touch lies in that, in the in-cell touch the function of the touch panel is embedded into liquid crystal pixels, while in the on-cell touch the function of the touch panel is embedded between a color-filter substrate (also referred to as a color filter) and a polarizer.
Specifically, the on-cell touch means that the function of the touch panel is integrated into the color-filter substrate. However, the in-cell touch means that a touch electrode assembly (which includes scanning electrodes or touch sensing electrodes) in the touch panel is formed on a plain glass (i.e., blank glass), which is then attached to a color-filter substrate, and then the resulted touch electrode assembly is embedded into liquid crystal pixels; alternatively, the touch electrode assembly in the touch panel is directly formed in a color-filter substrate or an array substrate. As compared with the on-cell touch panel, the built-in touch panel of in-cell touch has advantages of being thin and lightweight, which facilitates to reduce the manufacturing cost and decrease the thickness of the panel.
At present, for the purpose of making the panel of a capacitive touch screen thinner, there is provided an embedded capacitive touch screen in which touch electrodes are formed in the color-filter substrate or the array substrate. For example, a touch function is achieved by additionally adding touch electrodes directly onto an existing array substrate. That is, two layers of strip electrodes are formed in a manner of being noncoplanar and cross each other on a surface of the array substrate, and are generally made of indium tin oxide (ITO). Inductive capacitance occurs at a position where the two strip electrodes are noncoplanar and cross each other. It is determined whether a point is touched (i.e., a touch point) by detecting whether the value of the capacitance at the corresponding position changes or not.
As the resolution of display panel products increases, an increasing accuracy of the touch electrode is required, which makes a line-width of the strip electrode tend to decrease. However, according to the law of resistance (i.e., the following equation (1)):R=ρl/s=ρl/ab  (1)Where, for the strip electrode, R is the resistance value of the electrode, ρ is the resistivity determined by the material forming the electrode, l is the length of the electrode, s is the cross-sectional area of the electrode, a is the line-width of the electrode, and b is the thickness of the electrode.
It can be seen that, as the line-width a of the strip electrode decreases with other parameters remaining unchanged, the resistance value R of the electrode will increase accordingly, which causes the signal delay during a touch process to be increased and causes the touch sensitivity to be decreased. In order to decrease the resistance value R of the strip electrode, a solution which can be employed at present is to increase the thickness b of each of a touch scanning electrode and a touch sensing electrode. However, in a practical manufacturing process, the difficulty of a process for manufacturing a touch electrode as originally designed will increase if only the thickness b of each of the electrodes is increased. For example, during a film formation process for forming an amorphous ITO film, since a large thickness of a touch electrode is required, the ITO will be subject to a crystallization reaction so as to crystallize partially at a temperature equal to or higher than 150° C. Generally, an effect of an etching process (which is mainly a wet etching) performed on the amorphous ITO film is better than on the crystallized ITO film. The crystallization of the ITO will result in a problem of nonuniform etching in the subsequent etching process, which will cause a defect in the resultant product.
Therefore, the problem regarding how to not only reduce a signal delay during a touch process but also guarantee a rate of qualified product has becomes a technical problem to be solved urgently at present.